1. Field of the Invention
The present invention relates to semiconductor devices and fabrication methods thereof, and more particularly to semiconductor devices wherein the connection of the semiconductor device with the wiring is improved and to fabrication methods thereof.
2. Related Background Art
In recent years, as the higher integration of semiconductor devices has been made, the area of each part within a chip has been reduced, wherein it is an important problem to reduce the area of the wiring part because it occupies a large percentage of the chip area. Concerning the lead-out part to the wiring of a semi-conductor device or a so-called contact part, while it was conventionally practiced that after an ohmic contact material composed of group IV polycrystalline semi-conductor material was laid down at a position directly above the element, the electrode of a metal or metal silicide containing a low-melting metal such as Al and the group IV polycrystalline semiconductor material were joined off the position directly above the element. It is contemplated that a metal or metal silicide is also joined directly above the element at the same time.
On the other hand, a polycrystalline semiconductor material (e.g., group N) is undesirable to use as the lead-out wiring, because as the operation frequency of the element increases, the movement of carriers for carrying electric current can not follow it, whereby such a constitution is now being adopted that the electrode of metal or metal silicide is contacted directly above the element from the viewpoint of high speed operation.
However, a low-melting metal in the metal or metal silicide for use as low resistive wiring material greatly diffuses into polycrystalline semiconductor material, and when a metal or metal silicide contact is made directly above the element, the low-melting metal will diffuse into the element portion, bringing the above degradation of element characteristics in some cases. Accordingly, to suppress the diffusion of low-melting metal, a barrier metal may be disposed between the metal or metal silicide and polycrystalline semiconductor material. With this constitution, the diffusion of a low-melting metal is surely suppressed, and there is no degradation of element characteristics, but because of a step of depositing and patterning the barrier metal interposed, the process is more complex, with increased cost.